How does Mirrorweave work mtg

[Chameleon]

How does the card mirrorweave work in magic?

[Arix]

Exactly the way it says. You choose a target creature, then for the rest of the turn, every creature in play becomes a copy of that creature.

That said, it can create some weird situations, but you'll have to take those on a case-by-case basis rather than ask for an exhaustive list of everything it can do.

[Buddy]

what happens if after declaring attackers you make them all a copy of a creature with defender?

[Arix]

Nothing in particular. Defender only prevents a creature from being declared as an attacker. If the creatures have already been declared as attackers, gaining defender won't suddenly make them stop attacking.